Car batteries will usually last as long as they’re supposed to unless neglected. If your car came to you new off the lot, then there is no mystery involved in when and what kind of battery to choose when the time comes for some car maintenance.
The battery under the hood of that mint condition 1991 Dodge Colt Vista Wagon you just picked up off eBay may be of more uncertain origin. Worse is that your car might not even have the right battery for it. New car or used, the best time to choose and buy a car battery replacement is before the one presently under the hood gives up all together.
The car battery will tell you when this about to happen. Unless you left the lights on or there is an electrical short, automotive batteries will not generally suffer from sudden death. The classic warning sign of impending battery expiration is the starter laboring to turn over the engine in the morning. This laboring will slowly sound more difficult until nothing but a few sad clicks come from under the hood instead of the usual joyful cranking.
Checking battery life
A common and expensive do-it-yourselfer battery blunder is to assume the battery has quit altogether and replace it, only to discover a new but dead battery the following morning. If your vehicle seems to be laboring to turn the starter in the morning then first check the charging system. Many auto parts stores now have portable diagnostic equipment they can roll out to help you with this task. If the charging system checks out, then it’s time to run a car battery load test to determine if the battery needs maintenance or outright replacement. Also check for shorts. An electrical short can drain battery power while you sleep. A frayed wire grounding out against the frame or body of the car can create a circuit and drain battery power. A spent starter or starter solenoid can also mimic a dead battery. If battery replacement proves the best option, then making the best choice in batteries depends on several different factors.
Finding the right size battery
The first consideration is choosing the correctly sized battery for your vehicle. Car batteries are divided into what are called group sizes by automobile manufacturers to standardize battery sizes and prevent any square peg, round hole situations underhood. Fitment is an important concern. A perfect fit keeps the battery snug in the battery tray and working with the factory battery hold down system. This prevents battery damage by keeping vibration to a minimum. A car battery that is too small can rattle around in the battery tray and suffer short life. With the next step of the car battery buying process comes the realization that there is more than one battery in the display in the size required – but for some reason they have different prices.
Cold cranking amps
Before your inner cheapskate prevails, remember that a car battery must have enough power to turn over the engine. This cranking power is measured in battery Cold Cranking Amps (CCA), and is the standardized measured amount of cranking power that a given battery can deliver at 0 degrees Fahrenheit. CCA is of particular concern for those who live where winter temperatures can dip below zero. Engine and transmission oil become thick as molasses at these temperatures. Turning over the engine will sometimes require more CCA than measured at 0 degrees. Select a battery with a higher than required CCA rating if the vehicle is operated in colder than zero degree climates. Never select a car battery that has less than the CCA required by your engine. A few extra is better than too few.
This is a very important measurement. The car battery Reserve Capacity (RC) is the measure of battery strength when the going gets tough. RC is the amount of time the battery will deliver maximum amperage before discharging altogether. A good example of RC in practice is trying to start a stubborn engine. A car battery with a high RC rating will have enough power in reserve to get through tough situations such as stubborn engines or accidentally leaving the lights on while at the grocery store. Since the measure of RC is taken at warmer temperatures, it is of great importance to select a battery with a higher than required RC rating if the vehicle is operated in colder climates. The extra battery power waiting in reserve can help when you really need it most.
Removing and replacing a car battery
Hauling the car battery out of the engine compartment and into the auto parts store for a like-for-like comparison is one way to choose a battery, but it’s not always the most reliable method. Unless you purchased the vehicle new, there is no guarantee the correct battery was there in the first place. Compounding confusion is that time and battery acid are usually not kind to any identifying labels. This is where ideally you talk to a counter person and tell them what kind of car you have. The larger big box stores may have replaced humans with a frayed battery catalog, usually missing the one page that has which battery your vehicle uses. When buying a battery choose one with the highest quality and CCA/RC rating your budget can afford. Selecting more battery power than you need is generally better in the long run than choosing just enough. Knowledge is literally power when it comes to buying the right battery.